RNA interference (RNA i) is powerful technology for gene silencing and wide:'spread mechanism of gene regulation in Eucaryotes. RNAi gene silencing is a sequence specific transcriptional gene regulation (preventing the RNA synthesis) and post transcriptional RNA degradation (degrading mRNA and preventing protein synthesis), in which double stranded RNA is the interfering agent. Scientists have made striking progress in blocking gene expression and protein synthesis by using double stranded hairpin RNA in different living forms. The main features of RNAi are characterized as follows: High degree of specific, highly potent and effective (only a few dsRNA molecules per cell are required for effective interference), very sensitive (actively and quick response to interventing RNA like virus genes), silencing can be introduced at different developmental stages and may pass through generations. The great perspectives of RNAi technology for basic researches (identifYing gene function) and for different aspects of applications (virus disease control, development of transgenic organisms, biophannaceuticais and therapies for dangerous diseases like cancers, AIDS, etc.) have been analysed.